Problem getting nested Json in Store (different root for each Model)

How do I have to setup my store/reader and models to get the jsondata in? I tried different field mappings, jsonreader roots, but no success so far. I think the problem is, that the root nodes are not part of an array? I think I would multiple Reader.root properties, for each Model a different one. Is this possible somehow?

The only Idea I have myself in the moment, is to load the data via Ext.Ajax.request and fill the store manually, but I think there must be a more elegant solution. Any ideas?